If it were as simple as looking at a 'stuff' stat and only signing guys if it's higher than your available relievers then we wouldn't see teams consistently build good bullpens, while other teams like us consistently struggle.
If we truly thought that guys like Lovelady and Fluharty were better than the players available then that suggests that our projection systems are extraordinarily flawed. We have perhaps the league's finest pitching coach and still can't get results. I have doubts that it's a coaching problem.
That can be addressed, but in the meantime we should have acknowledged our failures and spent a bit of money to get better options in place. Chris Martin (1/5), Jonathan Loaisaga (1/3), and Justin Wilson (1/2) were some names that I suggested in the offseason. There's a good chance that we already have another win this season, had we signed one of them